1. Field of the Invention
This invention relates to the manufacture of cyclic polyolefinic hydrocarbons. It particularly relates to the reduction of organic compounds having at least one benzene ring in a calcium-amine-alcohol system to polyolefins of similar cyclic structures.
2. Description of the Prior Art
The principal method for reducing aromatic hydrocarbons is the Birch reduction method which employs sodium or lithium metal and liquid ammonia in the presence of an alcohol to produce diolefinic hydrocarbons. This process has the following disadvantages. Sodium metal is very reactive and requires a great deal of caution in use and handling. Liquid ammonia boils at -33.degree. C. and therefore is difficult to use on a large scale. It is obviously desirable to provide a safer and easier reduction process.
The reduction of aromaic compounds with calcium, ammonia, and ether has been reported by Dumanskii at al. J. Russ. Phys. Chem. Soc., 48, 994, (1916)., Kazanskii et al. J. Gen. Chem. (USSR), 8, 642, (1938), and Campbell et al. J. Am. Chem. Soc., 67, 282, (1945). The procedures reported by these workers are cumbersome and usually give products that are quite impure and difficult to separate. As a result, calcium reductions have never gained widespread acceptance and have been used only sporadically through the years.
The reduction of aromatic hydrocarbons by treatment with calcium metal in admixture with methylamine and ethylenediamine at -2.5.degree. C. is described by Benkeser et al. J. Org. Chem., 44, 3737 (Oct. 12, 1979). Unlike the invention described herein, alcohol was not utilized in that reducing system. Likewise, the use of inert abrasive particles to remove insoluble coatings that mask the calcium surface was not taught by the process described in that publication.
Filed of even date herewith is a patent application, Ser. No. 643,442, by the same inventors directed to the reduction of the same class of starting materials in the presence of ethylenediamine (or other analogous alkylene polyamine) and a 100% stoichiometric excess or more of calcium metal at ambient or somewhat elevated temperatures. Alcohol is not used in the reducing system of the companion application, and a large excess of calcium is used therein to compensate for insoluble coatings that form on the calcium metal surface. As will be seen below, other methods and operating conditions are employed in the invention of the present application.